If you're wondering which plants are absolutely deer-proof, wonder no more. There are none. If deer are hungry enough, they’ll eat just about anything. Preferences vary by deer species and the region in which they live, as well. That said, one excellent plant list can be found at the Rutgers New Jersey Agricultural Experiment Station. This Rutgers University webpage lists many common garden trees, perennials and shrubs and rates them on a scale of A (rarely damaged) through D (frequently severely damaged).
What Makes Up a Deer-Proof Plant?
In general, deer avoid plants with an unpleasant mouth-feel, such as hollies, and plants with strong fragrance, such as lavender. Your local extension agency may also offer a list of region-specific deer-resistant plants. These are usually locally native plants that have developed the ability to withstand deer browsing in order to survive.
Deer fencing can be a more reliable way to keep deer out. Keep in mind a deer will jump a fence shorter than nine feet. Manufacturers such as Deer Busters and Benner’s Gardens offer deer-specific fencing that’s made of black mesh. This offers you a way to create a tall-enough fence that you can still see through. The mesh blends into wooded backgrounds nicely. A fence five or six feet tall can be effective, though, if it is solid; deer will be afraid to leap without being able to see where they’ll land. If you desire a shorter fence, consider setting up two fences running parallel to each other, about four feet apart and four or five feet tall. Deer will know they need to clear both in one leap, but they’ll be reluctant to try.
If you have just a few plants you wish to protect, try deer-repelling sprays or granular shakers. Deer Stopper and Deer Solution, made by Messina Wildlife, Deer Scram, Liquid Fence and Deer Off are popular products.
Here's a link to a book full of deer-resistant advice you'll find useful, too!